chore: implement bucketized latency reporting for tool invocations (#822)

Author: ergunsh

src/main.ts

@@ -18,6 +18,7 @@ import {McpResponse} from './McpResponse.js';
 import {Mutex} from './Mutex.js';
 import {ClearcutLogger} from './telemetry/clearcut-logger.js';
 import {computeFlagUsage} from './telemetry/flag-utils.js';
+import {bucketizeLatency} from './telemetry/metric-utils.js';
 import {
   McpServer,
   StdioServerTransport,
@@ -221,7 +222,7 @@ function registerTool(tool: ToolDefinition): void {
         void clearcutLogger?.logToolInvocation({
           toolName: tool.name,
           success,
-          latencyMs: Date.now() - startTime,
+          latencyMs: bucketizeLatency(Date.now() - startTime),
         });
         guard.dispose();
       }

src/telemetry/metric-utils.ts

@@ -0,0 +1,16 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+const LATENCY_BUCKETS = [50, 100, 250, 500, 1000, 2500, 5000, 10000];
+
+export function bucketizeLatency(latencyMs: number): number {
+  for (const bucket of LATENCY_BUCKETS) {
+    if (latencyMs <= bucket) {
+      return bucket;
+    }
+  }
+  return LATENCY_BUCKETS[LATENCY_BUCKETS.length - 1];
+}

tests/telemetry/metric-utils.test.ts

@@ -0,0 +1,42 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import assert from 'node:assert';
+import {describe, it} from 'node:test';
+
+import {bucketizeLatency} from '../../src/telemetry/metric-utils.js';
+
+describe('bucketizeLatency', () => {
+  it('should bucketize values correctly', () => {
+    assert.strictEqual(bucketizeLatency(0), 50);
+    assert.strictEqual(bucketizeLatency(25), 50);
+    assert.strictEqual(bucketizeLatency(50), 50);
+
+    assert.strictEqual(bucketizeLatency(51), 100);
+    assert.strictEqual(bucketizeLatency(100), 100);
+
+    assert.strictEqual(bucketizeLatency(101), 250);
+    assert.strictEqual(bucketizeLatency(250), 250);
+
+    assert.strictEqual(bucketizeLatency(499), 500);
+    assert.strictEqual(bucketizeLatency(500), 500);
+
+    assert.strictEqual(bucketizeLatency(900), 1000);
+    assert.strictEqual(bucketizeLatency(1000), 1000);
+
+    assert.strictEqual(bucketizeLatency(2000), 2500);
+    assert.strictEqual(bucketizeLatency(2500), 2500);
+
+    assert.strictEqual(bucketizeLatency(4000), 5000);
+    assert.strictEqual(bucketizeLatency(5000), 5000);
+
+    assert.strictEqual(bucketizeLatency(6000), 10000);
+    assert.strictEqual(bucketizeLatency(10000), 10000);
+
+    assert.strictEqual(bucketizeLatency(10001), 10000);
+    assert.strictEqual(bucketizeLatency(99999), 10000);
+  });
+});